Re: [Qemu-devel] [PATCH v4] docs: add cpu-hotplug.txt

[Bharata B Rao]

On Tue, Aug 16, 2016 at 11:07:41AM +0800, Dou Liyang wrote:
> This document describes how to use cpu hotplug in QEMU.
> 
> Signed-off-by: Andrew Jones <address@hidden>
> Signed-off-by: Dou Liyang <address@hidden>
> ---
> Change log v3 -> v4
>   From David's advice
>     1. add spapr examples
>     2. Fix some comment
>   From drew's advice
>     1. Fix some syntax
> 
> Change log v2 -> v3:
>   From drew's advice:
>     1. modify the examples.
>     2. Fix some syntax.
> 
> Change log v1 -> v2:
>   From Fam's advice:
>     1. Fix some comment.
> 
> Change log v1:
>   From Igor's advice:
>     1. Remove any mentioning of apic-id from the document.
>     2. Remove the "device_del qom_path" from the CPU hot-unplug.
>     3. Fix some comment.
> 
>  docs/cpu-hotplug.txt | 132 
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 132 insertions(+)
>  create mode 100644 docs/cpu-hotplug.txt
> 
> diff --git a/docs/cpu-hotplug.txt b/docs/cpu-hotplug.txt
> new file mode 100644
> index 0000000..0c1bfe9
> --- /dev/null
> +++ b/docs/cpu-hotplug.txt
> @@ -0,0 +1,132 @@
> +QEMU CPU hotplug
> +================
> +
> +This document explains how to use the CPU hotplug feature in QEMU,
> +which regards the CPU as a device, using -device/device_add and
> +device_del.
> +
> +QEMU support was merged for 2.7.
> +
> +Guest support is required for CPU hotplug to work.
> +
> +CPU hot-plug
> +------------
> +
> +In order to be able to hotplug CPUs, QEMU has to be told the maximum
> +number of CPUs which the guest can have. This is done at startup time
> +by means of the -smp command-line option, which has the following
> +format:
> +
> + -smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads]
> +     [,sockets=sockets]
> +
> +Where,
> +
> + - "cpus"    sets the number of CPUs to 'n' [default=1].
> + - "maxcpus" sets the maximum number of CPUs, including offline VCPUs
> +   for hotplug.
> + - "sockets" sets the number of discrete sockets in the system.
> + - "cores"   sets the number of CPU cores on one socket.
> + - "threads" sets the number of threads on one CPU core.
> +
> +For example, the following command-line:
> +
> + qemu [...] -smp 3,maxcpus=8,sockets=2,cores=2,threads=2

This is not a valid topology on sPAPR. In the documentation, why not have
a bit more generic topology that is likely to work for most archs ?

Like -smp 4,maxcpus=8,sockets=2,cores=2,threads=2.

Regards,
Bharata.